Gr11 Excretion 2024 Teacher PDF

excretory system  excretion What are metabolic waste products? Metabolic waste products come from metabolic reactions reactions that occur within living cells/organisms that are essential for maintenance of life E.g. CO2, excess water and salts and nitrogenous wastes (u...

excretory system  excretion What are metabolic waste products? Metabolic waste products come from metabolic reactions reactions that occur within living cells/organisms that are essential for maintenance of life E.g. CO2, excess water and salts and nitrogenous wastes (urea, uric acid). the removal of the waste products of excretion metabolism from the body. the removal of undigested food from the alimentary canal of the Egestion body through the anus. This undigested food does not come from cells of the body.  excretion 4 main excretory substances waste product of CR Carbon transported in the blood from all the cells dioxide in the body to the alveoli of the lungs. excreted in the air that is exhaled. produced during CR water consumed in food and drink excess water is excreted in urine and sweat. Bile produced by the breakdown of pigments haemoglobin which takes place in the liver excreted in faeces. urea made in the liver from excess proteins that are consumed transported by blood excreted in urine  excretion deamination Is the process where an amino group (NH ) is removed from an amino acid molecule NH2 is cleaved off along with another hydrogen and they together form ammonia (NH ) Ammonia is very toxic so it is converted to urea (less toxic) by the addition of CO The left over amino acid molecule (without N) is converted to glucose ( glycogen and stored in liver) or fat excretion functions of the urinary system Excretion of nitrogenous waste substances Osmoregulation by regulating the water content of body fluids Regulates the salt content of body fluids Regulates the pH of body fluids POINT pH, osmoregulation, ions, nitrogenous waste, toxins)  excretion Structure of the urinary system Renal artery Kidneys Each kidney receives blood near the back of your via the renal artery abdomen. rich in oxygen and glucose They are surrounded by fat also contains toxins and which insulates the kidneys, nitrogenous wastes keeps them in position and absorbs shock. Renal vein Blood leaves the kidney through the renal vein deoxygenated blood no glucose,toxins or nitrogenous wastes Ureter Two narrow tubes that Hilum transports urine from Where the renal artery, the kidneys to the vein and ureter are bladder attached to the kidney Bladder Bladder stores urine temporarily Urethra Carries urine to the Sphincter muscle outside of the body control the opening of the bladder so that elimination of urine can be controlled. excretion Macroscopic structure  excretion Microscopic structure A kidney is made up of many tiny tubules called nephrons. Nephron = structural and functional unit of kidney Made up of Malpighian body (renal corpuscle) and renal tubule.  excretion 1. Malpighian body (Renal corpuscle) Made up of: 1. Bowman's capsule 2. Glomerulus Situated in the renal cortex Made up of bowman’s capsule & glomerulus The glomerulus (capillary network) sits inside the Bowman’s capsule cup shaped, hollow capsular space The Bowman’s capsule is made up of specialised cells podocytes The podocytes have filtration slits between them. Glomerular filtration takes place here a filtration unit It forces waste products out of the blood which passes through the glomerulus.  excretion Glomerular filtration Blood is carried by the afferent arteriole to the glomerulus. Efferent arteriole (exiting) is narrower than the afferent (arriving) blood in the glomerulus is under great hydrostatic/liquid pressure. Substances from the blood are filtered and forced out through capillary walls (which have tiny pores) and through the filtration slits of the podocytes and into the cavity of the Bowman’s capsule. Only substances small enough to fit through capillary- or slit pores pass into capsular space: fatty acids, amino acids, glycerol, glucose, salts, nitrogenous waste and water. The filtrate that passes into the capsular space = glomerular filtrate. Glomerular filtration isn’t a selective process (i.e. the filtrate does not only contain waste products, but useful ones as well).  excretion Adaptations of the malpighian body for glomerular filtration Blood pressure: Blood enters the glomerulus through a wider afferent arteriole and leaves through a narrower efferent arteriole. This builds up hydrostatic pressure in the glomerulus. This pressure forces the smaller components of blood plasma through the capillary pores and podocyte slits into the lumen of the Bowman’s Capsule Thin membranes: Glomerular capillary membranes are made up of a single layer of squamous epithelium. Inner lining of Bowman’s capsule is also only 1 cell layer thick there are only 2 layers of cells between the blood in capillaries and the filtrate in the capsule short distance and fast filtering. Large surface area: Cup shaped capsule and branched capillary network of glomerulus provide a large SA for maximum filtration. Porous membrane: Capillaries have numerous small pores (act as micro-filters), allowing only blood plasma to pass through them proteins and blood cells can’t = ultra-fine filtration Filtration slits: Podocyte layer of capsule has many filtration slits between podocyte cells. The filtered plasma passes easily through these slits into the capsular space. Podocyte cells have 4-6 feet-like projections (major processes) extending sideways and many finer projections (minor processes) that stretch towards the basement membrane.  excretion 2. Renal tubule Situated in: The cortex – proximal and distal convoluted cortex tubules The medulla – loop of Henle and collecting ducts The renal tubule is lined by cuboidal epithelial cells The renal tubule is made up of the: proximal convoluted tubule, medulla the loop of Henle (with a descending limb, hairpin bend and an ascending limb) distal convoluted tubule The DCT opens into the collecting duct These collecting ducts join to form the duct of Bellini in a pyramid and open into the calyces of the renal pelvis tubular reabsorption passive transports. is water is water more - absorbed. F permeable - > - selective (when in excess passes ↳ through] high. active Transpor to water is less absorbed As glomerular filtrate passes through the PCT, all the glucose, amino acids, vitamins are actively absorbed back into the peritubular capillaries that surround the PCT. Water follows the movement of these particles by osmosis (from a high Ψ inside the PCT to a low Ψ in the blood). After glucose, amino acids etc. have been actively reabsorbed, the glomerular filtrate is now called dilute urine Dilute urine still has a large amount of water as it enters the loop of Henle. The loop of Henle’s main job is to recover and conserve the amount of water that is needed by the body.  excretion Adaptations of the Proximal convoluted tubule for tubular reabsorption Tubules are convoluted this creates a large surface area which maximises absorption and slows down the movement of the filtrate --> allowing more time for absorption Microvilli on the surface of the cuboidal epithelial cells This further increases the surface area for maximum absorption Cuboidal epithelial cells contain a large number of mitochondria Supplies energy for active absorption (against the concentration gradient) Capillaries are in close contact with the PCT This reduces the distance for reabsorption of useful substances into the capillaries  excretion Blood supply to the Nephron Each Bowman’s capsule is supplied with blood by a branch of the renal artery, called an afferent arteriole which divides into a tangled network of capillaries called the glomerulus. The capillaries of the glomerulus rejoin to form the efferent arteriole. The efferent arteriole forms a network of capillaries running closely alongside the PCTs, LofH and DCTs. This network of capillaries is called the peritubular capillaries which eventually lead to the renal vein.  excretion tubular excretion Renal tubule cells don’t only re-absorb useful substances they also excrete wastes such as creatinine, drugs, ammonia, potassium, hydrogen and bicarbonate ions from the blood back into the tubule. The kidney tubules assist in regulating the pH of the blood: If the blood becomes too acidic If the blood becomes too aalkaline (low pH) (high pH) The concentration of H-ions in the The concentration of bicarbonate ions blood is high in the blood is high The cells of the tubules remove more The cells of the tubules remove more hydrogen ions from the blood and bicarbonate ions from the blood and pass them into the tubule, thus pass them into the tubule, thus reducing the H-ion concentration in reducing the bicarbonate the blood concentration in the blood The pH of blood returns to normal The pH of blood returns to normal  excretion The passage of urine to the bladder The fluid that leaves the collecting duct is called urine. Urine = concentrated solution of urea in water. Also contains salts, uric acid and creatinine.  excretion the role of loop of henle in conserving water Solution blood takes the Hypertonic potential Function of the Loop of Henle ↳ low water of solutes to recover and conserve the amount of water reading L lots that is needed by the body solution Hypotonic solutes ↳ low amount of ↳a high water potential sodium ions are actively pumped out of the ascending limb of the loop of HenlrE into the tissue fluid of the medulla ht This creates a lower water potential in the medulla medulla and a higher water potential in the ↑ notauniversa DCT and the collecting duct Water moves passively out of the DCT and Spe collecting duct (both permeable to water) into the medulla by osmosis The ascending limb of the loop of Henle is J impermeable to water Water from the medulla is reabsorbed back into the blood of the surrounding peritubular Luyper capillaries zosmosis The urine in the collecting ducts may be much f you have too don't create concentrated or dilute depending on whether water the body has an excess or shortage of water a hypertonic region The reabsorption of water from the DCT and CD is regulated by hormone called antidiuretic hormone. ↳ not universal  excretion homeostasis Process of maitaining a constant, internal environment within narrow limits, despite changes that take place internally and externally The kidneys maintain homeostasis by: Regulating the water content of the body through the action of the hormone ADH (osmoregulation) Controlling the pH of the blood Removing various cellular wastes and substances which are in excess (e.g. salts, uric acid and urea) osmoregulation Maintaining a constant internal water balance water loss -revents Hormone: Antidiuretic hormone (ADH) - to loose causes you & IOF of Water Produced: Hypothalamus Stored: Pituitary gland Target organ: Kidney --> DCT & CT  excretion Negative feedback mechanism - the role of adh in maintaining water levels When the body has too much water --> drinking lots of water/less sweating/ little exercise: Volume of water in the blood increases Osmoreceptors in the hypothalamus are stimulated Impulses are sent to pituitary gland to secrete less ADH into the blood walls of DCT and CD become less permeable to water less water leaves tubule via osmosis more water remains in the tubule more dilute urine which is excreted from the body less water is re-absorbed by capillaries level of water in blood decreases back to normal  excretion Negative feedback mechanism - the role of adh in maintaining water levels When the body has too little water --> excessive exercise/hot temperatures/increased sweating/or decreased water intake: Volume of water in the blood decreases Osmoreceptors in the hypothalamus are stimulated Impulses are sent to pituitary gland to secrete more ADH into the blood (ADH increases the number of water permeable channels in DCT and CD membrane) Walls of DCT and CD become more permeable to water More water leaves tubule via osmosis and is re- absorbed by capillaries More concentrated urine Level of water in blood increases back to normal  excretion Negative feedback mechanism - the role of adh in maintaining water levels  excretion homeostasis Process of maitaining a constant, internal environment within narrow limits, despite changes that take place internally and externally The kidneys maintain homeostasis by: Regulating the water content of the body through the action of the hormone ADH (osmoregulation) Controlling the pH of the blood Removing various cellular wastes and substances which are in excess (e.g. salts, uric acid and urea) salt balance Hormone: Aldosterone Produced: Adrenal gland Target organ: Kidney  excretion Negative feedback mechanism - the role of aldosterone in maintaining the salt balance of the blood When there is a shortage of sodium in the blood: More aldosterone is secreted Aldosterone stimulates the active re-absorption of sodium ions from the filtrate into the blood. less sodium ions are excreted sodium level returns to normal When there is an excess of sodium ions in the blood: Secretion of aldosterone decreases Less sodium is reabsorbed by blood capillaries more sodium is excreted. When sodium is in a tubule, water follows by osmosis the amount of urine excreted increases if the amount of sodium ions increase. the amount of sodium in the blood decreases back to normal  excretion Negative feedback mechanism - the role of aldosterone in maintaining the salt balance of the blood